This invention relates generally to large industrial flow control valves, and more particularly, to arm-driven sleeve valves.
Conventional sleeve valves have been employed to control the flow rate and head pressure of fluids in industrial piping systems. Sleeve valves are often utilized for their ability to operate without the moving components of the valve having to work against the head pressure of the fluid being supplied to the valve. A conventional arm-driven sleeve valve comprises a horizontally-oriented, tubular main body, and a tubular gate slidably engaged around the main body for controlling the flow rate of fluid from the valve.
The main body of a conventional arm-driven sleeve valve has a tubular wall that defines a fluid passage configured to receive fluid from a fluid supply line attached to a first axial end of the main body. An imperforate bulkhead at an opposite second axial end of the main body prohibits the fluid from flowing out the second axial end. At least one discharge opening extends through the tubular wall of the main body for discharging fluid from the fluid passage and into a tank or stilling well in which the valve is placed.
The sleeve valve is operated by axial movement of the tubular gate relative to the main body. The tubular gate is generally cylindrical and acts as a sleeve around the main body that can be axially moved between open and closed positions. In the closed position the gate is axially positioned so that all the discharge openings of the main body are axially between opposite ends of the gate. In the open position, the gate is axially positioned to one side of the discharge openings and thereby allows fluid to pass through the discharge openings of the main body into the tank or stilling well. Additionally, the gate can be variably positioned axially between the open and closed positions where the gate will partially cover the discharge openings to control the rate of fluid flow from the main body.
The axial movement of the gate of a conventional arm-driven sleeve valve is provided by a drive system comprised of a pair of swinging arms that translate rotational motion of a shaft into axial motion of the gate. In a convention arm-driven sleeve valve, the shaft of the drive system is mounted to the sleeve valve for rotation about the shaft's longitudinal axis. The arms are mounted to the shaft and extend away from the shaft axis such that as the shaft is rotated about its axis, a distal end of each of the arms will move along an arcuate path. By mounting the shaft to the sleeve valve in a manner such that the shaft axis is perpendicular to the longitudinal axis of the main body and attaching the distal end of each of the arms to opposite sides of the gate, the arcuate motion of the arms moves the gate along an axis of the main body.
Various types of drive mechanisms are used to provide the torque necessary to rotate the shaft of conventional arm-driven sleeve valves. Such drive mechanisms often include a worm gear connected to either a hand-crank or electromechanical motor. It is important to understand that when moving the gate, it is desirable that each arm exert an equal force on the gate to prevent the gate from binding with the main body. For this reason, the drive mechanism of a conventional arm-driven sleeve valve is typically configured to apply torque to the shaft at a location centrally between the arms such that torsional deflection of the shaft will not cause one arm to exert a greater axial force on the gate than the other. Alternative configurations of attaching drive mechanisms include applying torque equally to the opposite ends of the shaft.
While the above mentioned configurations of applying torque to the shaft of an arm-driven sleeve valve may prevent the gate from binding with the main body, such configurations have associated disadvantages. Configurations in which the torque is applied to the shaft centrally between the arms require the shaft to be positioned further from the gate to accommodate gearing or, alternatively, requires more complicated gearing than would otherwise be required. Applying torque to the ends of the shaft allows the shaft to be positioned closer to the gate but requires redundant components and some additional means of ensuring that equal torque is applied to each of the opposite ends of the shaft.